As a technology of Long Term Evolution-advanced (LTE-advanced), Carrier Aggregation (CA) is known (see, for example, Japanese Laid-open Patent Publication Nos. 2010-263256 and 2011-176687).
The carrier aggregation is a technique to communicate in wide frequency bands equal to or greater than 20 MHz by using plural Component Carriers (CC). An object of using the carrier aggregation is to improve the peak rate. The component carrier may also be called a “carrier”.
FIG. 1 illustrates an example radio communication system supporting the carrier aggregation. The radio communication system illustrated in FIG. 1 uses two component carriers. Those component carriers are expressed as a component carrier A and a component carrier B.
A radius of the cell of the component carrier A is greater than that of the cell of the component carrier B. The difference between the radiuses is based on the difference between the maximum transmission powers of the component carriers A and B.
In the example of FIG. 1, a part of the area of the component carrier A overlaps the area of the component carrier B of a radio base station 10. Therefore, a radio terminal located in the area of the component carrier B may use the bandwidths of the two component carriers A and B.
On the other hand, a radio terminal located in the area of the component A and out of the component area B may use the bandwidth of component carrier A. Namely, the radio terminal located in the area that is covered by component carrier A and that is not covered by the component carrier B may use the band width of the component A.
Reference may be made to Japanese Laid-open Patent Publication Nos. 2010-263256 and 2011-176687, 3GPP TS36.213 V10.4.0, December 2011, and 3GPP TS36.300 V11.0.0, December 2011.